1. Field of the Invention
This invention relates to a method for manufacturing a semiconductor device wherein a thin film is formed on a substrate.
2. Description of the Related Art
In semiconductor manufacturing processes, there is a CVD (Chemical Vapor Deposition) process in which a prescribed film formation process is performed on a surface of a substrate (a substrate to be processed which is based on a silicon wafer, a glass and the like, on which a fine electric circuit pattern is produced). In this CVD process, the substrate is loaded into a gas-tight reaction chamber, the substrate is heated by a heating means provided in the chamber, and a chemical reaction is allowed to occur while introducing a film formation gas on the substrate, to uniformly form a thin film on the fine electric circuit pattern provided on the substrate. In such a reaction chamber, the thin film is also formed on a structure besides the substrate. In a CVD apparatus as shown in FIG. 19, a shower head 6 and a susceptor 2 is provided in a reaction chamber 1, and a substrate 4 is disposed on the susceptor 2. A film formation gas is introduced into the reaction chamber 1 through a raw material supply tube 5 which is connected to the shower head 6, and supplied on the substrate 4 through a plurality of apertures 8 which are provided in the shower head 6. The gas which is supplied on the substrate 4 is subjected to an exhaust process through an exhaust tube 7. In addition, the substrate 4 is heated by a heater 3 which is provided below the susceptor 2.
As such a CVD apparatus, there is an ALD (Atomic Layer Deposition) apparatus or an MOCVD (Metal Organic Chemical Vapor Deposition) apparatus for forming an amorphous HfO2 film or an amorphous Hf silicate film using an organic chemical material as a film formation raw material (the amorphous HfO2 film and the amorphous Hf silicate film being hereinafter simply abbreviated as an HfO film). Here, the differences between the CVD method performed by the MOCVD apparatus and the ALD method performed by the ALD apparatus are as follows. The ALD method is performed at a low process temperature and under a low pressure to form a film by one atomic layer at a time. On the contrary, the CVD method is performed at a higher process temperature and under a higher pressure than those of the ALD method to form a film by approximately a ⅙ atomic layer to tens of atomic layers at a time.
The film formation raw material which includes:
Hf[OC(CH3)3]4 (hereinafter abbreviated as Hf-(OtBu)4);
Hf[OC(CH3)2CH2OCH3]4 (hereinafter abbreviated as Hf-(MMP)4) where MMP: methylmethoxypropoxy;
Hf[Oxe2x80x94Sixe2x80x94(CH3)3]4; and the like, is used.
In such materials, most organic materials, for example, Hf-(OtBu)4 and Hf-(MMP)4, are in a liquid phase at ordinary temperature and ordinary pressure. As a result, for example, Hf-(MMP)4 is heated and changed into a gas due to a vapor pressure and is utilized. Utilizing such a raw material and using the above-described CVD method, an HfO film is formed, for example, at a substrate temperature of 450xc2x0 C. or lower. This HfO film contains impurities such as CH, OH and the like, in large quantity, for example, in an amount of several percent (%), which result from the organic material. Consequently, as a classification indicating an electrical property of a substance, the HfO film belongs to a semiconductor or conductor which is contrary to the intention of ensuring an electrical insulator.
In order to ensure electrical insulation of such a thin film and stability of the film, conventionally, an attempt has been made to allow C and H to leave the HfO film so as to convert it into an densified stable insulator thin film, by performing on the HfO film a rapid annealing treatment (hereinafter abbreviated as an RTA (Rapid Thermal Annealing)) at a temperature of 650xc2x0 C. to 800xc2x0 C. in an atmosphere of O2 or N2. Here, an aim of the RTA is to allow the impurities such as C, H and the like, in a film to leave the film and is to densify the film. Although the densification is not performed up to crystallization, the densification is performed in order to allow a mean interatomic distance in an amorphous state to be shorter.
In FIG. 20, there is shown a cluster apparatus construction in a conventional method for forming an HfO film. A substrate is loaded into a load-lock chamber 32. In a first reaction chamber 33, a substrate surface treatment such as RCA cleaning (a typical cleaning method based on hydrogen peroxide) and the like, is performed. In a second reaction chamber 34, an HfO film according to a method corresponding to the above-described method is formed. In a third reaction chamber 35, an RTA treatment (an impurity removal, thermal annealing treatment) is performed. In a fourth reaction chamber 36, an electrode (for example, a poly-Si thin film and the like) is formed. The substrate on which the electrode is formed is unloaded from the load-lock chamber 32 to an outside of the apparatus. The above carrying-in and carrying-out are performed using a substrate transfer robot 31 provided in a substrate transfer chamber 30.
In the third chamber 35, when C and H are allowed to leave the HfO film by the RTA treatment, there arises a problem that a surface state of the HfO film loses evenness and changes into an uneven surface state. Further, the HfO film tends to partially crystallize by the RTA treatment so that a large current becomes apt to pass through a crystal grain boundary to cause a problem that the insulation and stability of the film are impaired, which is contrary to the intention. These problems which are not limited to an insulator are common to all thin film deposition methods which utilize an ALD method or an MOCVD method in which a organic chemical material is used.
Moreover, in the second reaction chamber 34, a thin film is also formed on a structure besides a substrate. This is referred to as an accumulated film in which a large quantity of C and H are also mixed. As a result, amounts of C and H leaving the accumulated film increase with increasing number of the processed substrates, and amounts of C and H mixed and contained in the HfO film gradually increase with increasing number of the processed substrates. Due to this phenomenon, it is very difficult to allow the quality of the continuously produced HfO films to be constant. Therefore, in order to solve the critical phenomenon, it becomes necessary to frequently practice a removal process of an accumulated film by self-cleaning, which becomes a factor that decreases productivity.
As stated above, in the conventional technique for forming an amorphous thin film, there are problems that the surface state of an HfO film loses evenness by an RTA treatment and changes into an uneven surface state, and that the HfO film partially crystallizes by the RTA treatment so as to allow a crystal grain boundary to occur so that the insulation and stability of the film are lowered.
Furthermore, in order to allow the quality of continuously produced HfO films to be constant, it is necessary to frequently practice a cleaning process of an accumulated film in which a large quantity of C and H are mixed. As a result, the productivity is reduced.
In addition, as a thin film formation technique, which does not relate to an HfO film, a method for repeating in a same reaction chamber a Ta2O5 film formation and a modification process two or more times (for example, refer to Patent Document 1), a method for repeating in a same reaction chamber a film formation process of a high dielectric constant oxide film and a ferroelectrics oxide film and a heat treatment with plasma generated by using an oxidative atmospheric gas two or more times (for example, refer to Patent Document 2), and a method for repeating a metal film formation process and a metal nitride film formation process by introducing a nitriding material gas two or more times (for example, refer to Patent Document 3) are known.
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-50622
[Patent Document 2]
Japanese Patent Application Laid-Open No. 11-177057
[Patent Document 3]
Japanese Patent Application Laid-Open No. 11-217672
However, when a metal oxide film is formed using the conventional techniques described in the above-stated Patent Documents 1 to 3, the metal oxide film is formed using a gas containing an oxygen atom in addition to a raw material during the film-forming step so that a specific element in the metal oxide film can not be removed effectively during the film-modifying step thereby providing insufficient modification of the film.
Moreover, since the film formation gas and the reactant are supplied through different supply ports, foreign substances which adhere to the inside of the supply ports can not be restrained from falling down on the substrate, and even if cleaning is performed, the cleaning gas and by-products which are adsorbed onto the inside of the supply ports are removed insufficiently.
Furthermore, if a thin film is formed and annealed in one apparatus, subsequently taken out from the apparatus and provided with an electrode formed thereon in a different apparatus, the problem that a throughput is reduced is caused.
An object of the present invention is to provide a method for manufacturing a semiconductor device wherewith, by resolving the problems with the prior art noted in the foregoing, a specific element in a metal oxide film can be removed effectively during a film-modifying step. A further object of the present invention is to provide a method for manufacturing a semiconductor device wherewith foreign substances which adhere to an inside of supply ports can be restrained from falling down on a substrate, and a cleaning gas and by-products which are adsorbed onto the inside of the supply ports due to cleaning can be removed. A further object of the present invention is to provide a method for manufacturing a semiconductor device wherewith a specific element in a film containing Hf can be removed rapidly. A further object of the present invention is to provide a method for manufacturing a semiconductor device wherewith a throughput can be enhanced.
A first invention is a method for manufacturing a semiconductor device comprising the steps of: forming a metal oxide film on a substrate using a raw material gas obtained by vaporizing a raw material containing an oxygen atom and a metal atom and without using a gas containing an oxygen atom except said raw material gas; and modifying the metal oxide film which is formed in the film-forming step, using a reactant which is different from said raw material gas, wherein the film-forming step and the film-modifying step are successively repeated two or more times. Since a metal oxide film is formed on a substrate without using a gas containing an oxygen atom except a raw material gas in a film-forming step, even though the raw material gas is used that is obtained by vaporizing a raw material containing an oxygen atom and a metal atom and being liable to allow a specific element to be contained in the film, the specific element in the film can be removed effectively so as to make the film easy to modify. In addition, since a film-forming step and a film-modifying step are repeated successively, a specific element in the film formed in the film-forming step can be removed rapidly so as to modify the film. Moreover, since a film-forming step and a film-modifying step are repeated successively two or more times, a film with a prescribed film thickness can be formed, and also a removed amount of a specific element in the formed film can be increased so as to modify the film sufficiently, in comparison with the case wherein a film with a prescribed film thickness is formed at a time, and then the film-modifying step is performed.
A second invention is a method for manufacturing a semiconductor device according to the first invention, wherein the film-forming step and the film-modifying step are performed in a same reaction chamber. When the film-forming step and the film-modifying step are performed in the same reaction chamber, a temperature drop of the substrate does not occur between the steps. As a result, a temperature raising time for processing the substrate again becomes unnecessary so that the temperature raising time of the substrate can be saved so as to provide good efficiency in processing. In addition, since the substrate remains in the same reaction chamber, the surface of the formed film becomes difficult to contaminate.
A third invention is a method for manufacturing a semiconductor device according to the first invention, wherein the metal atom is Hf, and the metal oxide film is a film containing Hf. In the case of using a raw material containing a metal atom as a raw material, a gas containing an oxygen atom such as an oxygen gas and the like is typically used along with the raw material. In particular, however, in the case that the metal atom is Hf and the metal oxide film is a film containing Hf, a specific element in the film which is formed without using a gas containing an oxygen atom rather than with using a gas containing an oxygen atom can be removed effectively so as to modify the film.
A fourth invention is a method for manufacturing a semiconductor device according to the first invention, wherein the raw material is Hf[OC(CH3)2CH2OCH3]4, and the metal oxide film is a film containing Hf. In the case of using a organic raw material as a raw material, a gas containing an oxygen atom is typically used along with the raw material. In particular, however, in the case of using Hf[OC(CH3)2CH2OCH3]4, a mixing amount of a specific element (an impurity) such as C, H or the like can be small without using a gas containing an oxygen atom rather than with using a gas containing an oxygen atom.
A fifth invention is a method for manufacturing a semiconductor device according to the first invention, wherein the metal atom is Hf, and the metal oxide film is a film containing Hf, and a film thickness of the metal oxide film which is formed in one film-forming step is 0.5 xc3x85-30 xc3x85. In the case that a film thickness of a film containing Hf which is formed in one film-forming step is 0.5 xc3x85-30 xc3x85 (a ⅙ atomic layer to ten atomic layers), even though an impurity is contained in the film, it is possible to maintain a state of the film in which the film is difficult to crystallize, and performing the modification process in such a state can remove the impurity so as to make the film easy to modify.
A sixth invention is a method for manufacturing a semiconductor device according to the second invention, wherein the raw material gas supplied to the substrate in the film-forming step and the reactant supplied to the substrate in the film-modifying step are supplied through a same supply port. If the raw material gas supplied to the substrate in the film-forming step and the reactant supplied to the substrate in the film-modifying step are supplied through a same supply port, a metal oxide film can be deposited such that foreign substances which adhere to the inside of the supply port are covered with the deposited metal oxide film, so that the foreign substances can be restrained from falling down on the substrate. In addition, in the case that the reaction chamber is cleaned with a cleaning gas, the cleaning gas and by-products which are adsorbed onto the inside of the supply ports can be removed.
A seventh invention is a method for manufacturing a semiconductor device according to the second invention, wherein the raw material gas supplied to the substrate in the film-forming step and the reactant supplied to the substrate in the film-modifying step are supplied through different supply ports, respectively, wherein, when the raw material gas is supplied to the substrate through the supply port for the raw material gas in the film-forming step, a nonreactive gas is supplied to the supply port for the reactant, and wherein, when the reactant is supplied to the substrate through the supply port for the reactant in the film-modifying step, a nonreactive gas is supplied to the supply port for the raw material gas. Thus, the raw material gas and the reactant are supplied through different supply ports respectively, and a nonreactive gas such as an inert gas and the like is supplied in the respective steps through the supply port for one of the steps which is not involved in the currently performed step. This can also restrain the accumulated film from forming onto the inside of the supply ports.
An eighth invention is a method for manufacturing a semiconductor device according to the second invention, wherein, when the raw material gas is supplied to the substrate in the film-forming step, the reactant used in the film-modifying step is exhausted without stopping the supply of the reactant such that the reactant bypasses the reaction chamber, and wherein, when the reactant is supplied to the substrate in the film-modifying step, the raw material gas used in the film-forming step is exhausted without stopping the supply of the raw material gas such that the raw material gas bypasses the reaction chamber. In this way, if the reactant in the film-forming step and the film formation gas in the film-modifying step are kept flowing to bypass the reaction chamber without stopping their supply, the film formation gas or the reactant can be immediately supplied to the substrate only by allowing the flow bypassing the reaction chamber to switch from the bypassing state to the flowing state into the reaction chamber. As a result, a throughput can be enhanced.
A ninth invention is a method for manufacturing a semiconductor device according to the second invention, wherein an exhaust line for exhausting an interior of the reaction chamber in the film-forming step and an exhaust line for exhausting the interior of the reaction chamber in the film-modifying step are provided with a trap for use shared between both the steps. Since exhaust lines are provided with a trap, an entry of the raw material into an apparatus for removing hazardous materials and an exhaust pump in communication with the exhaust lines can be reduced, and a maintenance cycle of a substrate processing apparatus can be extended. In addition, since the trap is used in common between both the steps, the maintenance becomes simple.
A tenth invention is a method for manufacturing a semiconductor device according to the second invention, wherein the cleaning step is a step of removing a film which adheres to an inside of the reaction chamber using a cleaning gas which is activated by plasma, wherein the reactant used in the film-modifying step is a gas which is activated by plasma, and wherein a plasma source used for activating the gas in the film-modifying step and a plasma source used for activating the cleaning gas in the cleaning step are one plasma source shared with both the steps. Since one plasma source is shared with the reactant activation and the cleaning gas activation, control of the plasma source becomes easy and a semiconductor device can be manufactured at a low cost.
An eleventh invention is a method for manufacturing a semiconductor device according to the first invention, wherein the reactant contains an oxygen atom. If the reactant contains an oxygen atom, the film-modifying step of a specific element can be efficiently performed immediately after the metal oxide film formation.
A twelfth invention is a methods for manufacturing a semiconductor device according to the first invention, wherein the reactant comprises a gas obtained by activating a gas containing an oxygen atom. If the reactant is a gas obtained by activating a gas containing an oxygen atom by plasma, the film-modifying step of a specific element can be more efficiently performed immediately after the metal oxide film formation.
A thirteenth invention is a method for manufacturing a semiconductor device according to the first invention, wherein the film-forming step and/or the film-modifying step is performed while rotating the substrate. Since the step or steps are performed while rotating the substrate, a specific element in the film can be quickly removed uniformly so as to modify the film.
A fourteenth invention is a method for manufacturing a semiconductor device according to the second invention, further comprising the steps of: transferring the substrate from the reaction chamber via a transfer chamber to a different reaction chamber without exposing the substrate to an ambient atmosphere after forming the metal oxide film on the substrate by repeating the film-forming step and the film-modifying step, and forming in the different reaction chamber an electrode on the metal oxide film formed on the substrate, wherein, after forming the metal oxide film, the electrode is formed without performing an annealing step as a different step from the electrode formation step, and wherein the steps from the metal oxide film formation to the electrode formation are performed in a same apparatus. Since the steps from the metal oxide film formation to the electrode formation are performed in a same apparatus, the temperature raising time of the substrate can be saved in comparison with the case wherein the electrode formation is performed in a different apparatus. Moreover, the electrode can be formed on the film surface which remains in a clean state. Furthermore, since the metal oxide film is densified by thermal annealing performed when forming the electrode, the film becomes difficult to contaminate.
A fifteenth invention is a method for manufacturing a semiconductor device comprising the steps of: forming a thin film on a substrate by supplying a film formation gas to the substrate; and modifying the thin film which is formed in the film-forming step, by supplying a reactant which is different from said film formation gas, wherein the film-forming step and the film-modifying step are successively repeated in a same reaction chamber two or more times, and wherein the film formation gas supplied to the substrate in said film-forming step and the reactant supplied to the substrate in said film-modifying step are supplied through a same supply port. Since a film-forming step and a film-modifying step are repeated successively, a specific element in the film formed in the film-forming step can be removed rapidly so as to modify the film. In addition, since a film-forming step and a film-modifying step are repeated successively two or more times, a film with a prescribed film thickness can be formed, and also a removed amount of a specific element in the formed film can be increased so as to modify the film sufficiently, in comparison with the case wherein a film with a prescribed film thickness is formed at a time, and then the film-modifying step is performed. Moreover, if the raw material gas supplied to the substrate in the film-forming step and the reactant supplied to the substrate in the film-modifying step are supplied through a same supply port, a thin film can be deposited such that foreign substances which adhere to the inside of the supply port are covered with the deposited thin film, so that the foreign substances can be restrained from falling down on the substrate. Furthermore, in the case that the reaction chamber is cleaned with a cleaning gas, the cleaning gas and by-products which are adsorbed onto the inside of the supply ports can be removed.
A sixteenth invention is a method for manufacturing a semiconductor device comprising the steps of: forming a film containing Hf on a substrate using a raw material gas obtained by vaporizing a raw material containing Hf; and modifying the film containing Hf which is formed in the film-forming step, using a reactant which is different from said raw material gas, wherein the film-forming step and the film-modifying step are successively repeated two or more times. Since a film-forming step and a film-modifying step are repeated successively, a specific element in the film containing Hf formed in the film-forming step can be removed rapidly so as to modify the film. In addition, since a film-forming step and a film-modifying step are repeated successively two or more times, a film containing Hf with a prescribed film thickness can be formed, and also a removed amount of a specific element in the formed film can be increased so as to modify the film containing Hf sufficiently, in comparison with the case wherein a film containing Hf with a prescribed film thickness is formed at a time, and then the film-modifying step is performed.
A seventeenth invention is a method for manufacturing a semiconductor device according to the sixteenth invention, wherein a film thickness of the film containing Hf which is formed in one film-forming step is 0.5 xc3x85-30 xc3x85. In the case that a film thickness of a film containing Hf which is formed in one film-forming step is 0.5 xc3x85-30 xc3x85, namely, a ⅙ atomic layer to ten atomic layers, even though an impurity exists in the film, it is possible to maintain a state of the film in which the film is difficult to crystallize, and performing the modification process in such a state can remove the impurity so as to make the film easy to modify.
An eighteenth invention is A method for manufacturing a semiconductor device comprising the steps of: forming a thin film on a substrate by supplying a film formation gas to the substrate; modifying the thin film which is formed in the film-forming step, by supplying a reactant which is different from said film formation gas; transferring the substrate from the reaction chamber via a transfer chamber to a different reaction chamber without exposing the substrate to an ambient atmosphere; and forming in the different reaction chamber an electrode on the thin film formed on the substrate, wherein, after forming a thin film on the substrate by successively repeating in a same reaction chamber the film-forming step and the film-modifying step two or more times, the substrate transfer step and the electrode formation step are performed, and wherein, after forming the thin film by repeating the film-forming step and the film-modifying step two or more times, the electrode is formed without performing an annealing step as a different step from the electrode formation step, and wherein the steps from the thin film formation to the electrode formation are performed in a same apparatus. Since the steps from the thin film formation to the thin film modification and the electrode formation are performed in a same apparatus, the temperature raising time of the substrate can be saved in comparison with the case wherein the thin film modification or the electrode formation is performed in a different apparatus. Moreover, a specific element in the film can be removed rapidly so as to modify the film, and the electrode can be formed on the thin film surface which remains in a clean state. Furthermore, since the thin film is densified by thermal annealing performed when forming the electrode, the thin film becomes difficult to contaminate.
A nineteenth invention is a substrate processing apparatus comprising: a reaction chamber in which a substrate is processed; a first supply port through which a raw material gas is supplied into the reaction chamber, the raw material gas being obtained by vaporizing a raw material containing an oxygen atom and a metal atom; a second supply port through which a reactant is supplied into the reaction chamber, the reactant being different from the raw material gas; an exhaust port through which an inside of the reaction chamber is exhausted; and a controller for controlling a film-forming step and a film-modifying step such that the film-forming step and the film-modifying step are successively repeated two or more times, wherein the film-forming step is a step of forming in the reaction chamber a metal oxide film on a substrate without using a gas containing an oxygen atom except the raw material gas, and wherein the film-modifying step is a step of modifying the metal oxide film which is formed in the film-forming step, using the reactant which is different from the raw material gas. Since a substrate processing apparatus comprises a controller for controlling a film-forming step and a film-modifying step such that the film-forming step and the film-modifying step are successively repeated two or more times, the above-stated method for manufacturing a semiconductor device can be easily performed using the substrate processing apparatus.
In the first invention, the second invention, the sixth invention to the fifteenth invention, the eighteenth invention and the nineteenth invention, as stated above, the film which is formed in the film-forming step is not limited to a film containing Hf. On the other hand, in the third invention to the fifth invention, the sixteenth invention and the seventh invention, the film which is formed in the film-forming step is limited to a film containing Hf. Examples of the films containing Hf are HfO2, HfON, HfSiO, HfSiON, HfAlO and HfAlON. In addition, examples of the films except the films containing Hf are as follows:
TaO film (tantalum oxide film) using PET(Ta(OC2H5)5),
ZrO film (zirconium oxide film) using Zr-(MMP)4,
AlO film (aluminum oxide film) using Al-(MMP)3,
ZrSiO film (Zr oxide silicate film) and ZrSiON film (Zr oxynitride silicate film) using Zr-(MMP)4 and Si-(MMP)4,
ZrAlO and ZrAlON films using Zr-(MMP)4 and Al-(MMP)3,
TiO film (titanium oxide film) using Ti-(MMP)4,
TiSiO and TiSiON films using Ti-(MMP)4 and Si-(MMP)4, and
TiAlO and TiAlON films using Ti-(MMP)4 and Al-(MMP)3.